Method of oxidizing ammonia



lytically oxidizing suitable carriers.

' UNITED STATES PATENT ornrcn.

ALEXANDER ctAssnngor AAcnEn, GERMANY, Assmnon, B mnsnn A'ssrennnn'rs,

' To run cnEmcAn FOUNDATION, 11m, A conronA rron or DELAWARE;

mnrnon'or' oxrmzme 'AnmonIA.

No Drawing.

To all whom it may concern:

Be it known, that I, ALnxANDER CLAssnn,

a subject of the German Emperor, and'resident of Aachen, Germany, have-invented certain new and useful lmprovenrientso in- Methods of. Oxidizing Aminonia, of which the following is a specification.

My inventlon relates to a method of cataammonia gas with a wow to obtaining nitrogen oxids.

It is Well known that by passin a mixture of ammonia. and air over cata ytically. active substances at an elevated temperature Quite a number of catalytically active; substances, most of them metals and metallic oxids, have been proposed for carrying outthis process, such substances being" designed to/be employed either alone or in combination with I have now ascertained that the chemical nature of the carrier is of paramount in1-, portance with regard to the result of the catalytic oxidation which is to take place.

IFOI instance, if catalytically active sub-.

stances such as oxid of copper or someother suitable metallic oxlds are used on the one hand in combination with wellknown carmagnesium, barium, calcium astonishin 5 -oxidation of ammonia.

riers .such as asbestos, fire-bricks, meerschaufn, clay and the like, and on the other. hand 'with basic carriers such as the oxid of zinc or the like, there will result in the latter case an output of nitrogen oxids.

Upon further investig in fact'I have ascertalned that the favor-' ab e action of basic carriers is. not l1m1ted to their combination with metallic oxids but will take place also in the case that the basic carriers are combined with other catalytically active substances suitable for the In consequence thereof the basic substances'in question can not.be considered merely as carriers as far as the reaction in question is concerned, and it seems that the good results obtained with their aid are obtained through a combination efifect between the catalytically active substances proper (metallic oxid's, metals and the like) and the basic substances. The,

' success obtained. by the combined application of these substances is the more surpris ing as the 'baslc substances in questlon do tests.

increase" of the catalytic 'efl'ect which wil appear as a considerably hlghei' r. quantities of'the catalytically active subatiiig this astonish- ,stanoes proper. and the carriers. In gen-f n es ium re p of magnesla and, five to thirty-five grams' Specification of Letters Patent. Patented NOV. 18,1919. I Application 'nled January 2;, 1916. Seria1 No. 74,007.

- not by themselves exert any catalytic action -1n the oxidation of ammonia.

' manganese, iron, IILthGHilIm, and chromium, -wh1ch'are sultable for oxldlzmg ammonia gas, in combination with highly basic substances, referably such as consist of or' contain' hig ly basic metal oxids. On the basis of my invention it'is easy to prepare a great number of efficient catalyticagents by simple The catalytically' active substances proper, such as nietals metallic osids or other combinations of metals; may be em loyed either singly 'or in. plurality and int e latter case they may either form a mixture or an alloy or a chemical combination. In a like .mannerthe basic substances serving as carriers may be em loyed either singly. orin plurality, in the atter case as 'a mixture or under the form ofa'chemical combination, and they mayzlas well be combined with other substances in. the manner 'men tioned ab'ove,provided their basic character is retained- Thus for instance alum'inates arelhighly efiicient carriers for use in carrymg out the present invention.

Ihave' further ascertained'thatthe favorable action of the, contact bodies or cata-.- lytlcally active combinations obtainedin acpendent to a high degree on the relative cordance ,yviththe present method are de-" i eral it is preferable 'to employ the carrier.

substance ro r. For instance an eflicient catalyst o xld of copper-and oxid of magires about 'wo hundred grams of solid nitrate of-copper."

I havefurther ascertam dtliat apart from the basic nature of the contact-carrier also its physical qualities play an important role.

for instance a specifically heavier magnesite is a better contact carrier than a specifically lighter one. In consequence thereof I prefer' densifying porous contact carriers, for instance by slntering them by heating to a high temperature or by impregnating them with a metal salt solution and then heatlng them. Thus a highly efiicient carrier is obtained from magnesium oxid by impregnat-- ingthe roasted oxidwith a solution of magnesi um iiitrate and transforming the latter intoj oxid by roasting the mass By this treatment an artificial densification is caused to take place within the pores of the oxid. by

the oxid formed from the nitrate.

As. has been mentioned the basic carriers may be combined. with all kinds of catalysts. The catalysts most suitable for use in this combination are forinstance the different metal oxids having catalytic qualities,

chromates, chromites and also metallic cata"- .lysts the foremost of which are certain preleaving behind -a' strongly'basic oxid after roasting, and the carrier is then immersed in the solution .of a suitable manganese salt. After drying and roasting a vmass is obtained which contains besides the catalyst proper (M11 0 thebasic oxid corresponding to the salt employed, such as manganese oxid-zinc oxid, manganese oxid-magnesium oxid or the like. Preferably the different substances are a plied -in such -a relation that a correspon ing excess of basic oxid is resent. o

'Example III: Magnesia'grains are impregnated at first with a solution of nitrate of lead and 'then with a solution of potasoxid of copper cata yet the magnesia grains sium bi'chromate according to the quantity of lead nitrate employed. After drying and roasting achromateof lead catalyst is ob-" ,tained.

riers will furnish good catalysts for the I preparation of nitrogen oxids. Combinatlons of chromium oxid and zinc have proved to be especially eflicient.

In order to obtain a calcium-ochromite catalyst magnesia or another suitable carrier 1s impregnated with a solution of chrome-alum and then with the solution of a calcium salt, ammonia is then added and the mass is dried and roasted.

Example V: F 'nely powdered ruthenium I is intimately mixed with magnesia grains,

other contact substances being added ifv necessary, such a substance being for instance finely divided silver, preferably colloidal "silver.

Example VI: Magnesia grains are impregnated with a solution of silver nitrate, the nitrate being thenconverted by the appllcation of heat into-metallic silver.

Examplev VII: Magnesium oxid is im- 'n'um-ammonium-ch'lorid or iridium ammonlum-chlorid. and then heated to' red heat. In this manner catalysts of i on basic carriers are obtained.

In all cases it is preferable to so vary the relative quantities that the basic carrier is 1n great excess of the catalyst proper. The best relation in each case can easily [)3 ascertained by testing. I

' pregnated with a watery solution of platiprecious metals The description of the invention and the examples given above make it easy to comb ne all kinds of catalysts. Insteadof combm ng the desired catalyst directly with the desired basic carrier, it is preferable in many cases to have the catalyst or the basic car- .rier or both of them yformed only at the moment,- when the contact substance, is form1ng, such as by the decomposition of suitable salts. One may as 'well employ natlve ores such as magnesium carbonate, dolom1te, hydrozmci-te or zinc-spar which will be converted by heating .into the desired highly bas c metal oxids. Such constituents as may be wanting can be added in the form of corresponding salt solutions, the whole then being heated or treated in any other suitable way.

In some cases, the catalyst proper such as for instance a chromite may be prepared on i In order ,to prep re a chromate of lead'-' the basic carrier by converting art of id are impregnated first witha solution of lead nitrate, then WltlLa'SOllitlOIL of copper Iii I trate and then with potassiumbichromate, whereupon they are dried and roasted; In-

stead of chromate oflead other combinations of chromic acid with metals,'such as, silver, bismuth, barium and others may be used either alone or'mixed with. each? other or mixed with'other'catalysts.

Chromite ofcalcium or of magnesium -or for cordance with the present invention it is doubtful whether the catalyst deposited on the basic carrier is combined with it merely 1n a physical way or whether it has entered into a chemical combination, .such as a Example IY .Chrom1te s such as the;

double salt with part ofthe carrier, such combination then acting as a catalyst as 180' Well. As has already been explained at the beginning,. aso called couple-efi'ect seems to take place between the catalyst on the one hand and the basic carrier on the other hand, and it is diflicult to decide whether one component of the couple is the substance directly deposited on or formed upon the carrier'or whether it is a combination of said substance with part of the carrier. In any case it s. important that the other componentsihave basic qualities. It is therefore to be understood that by an expl ssion such as catalytically active substances associated with basic substances I include either a chemical substances.

I wish it to be understood that by no means an metal or any combination of a metalwil in combination with a highly or physical combination of these 2U basic carrier, form an excellent catalyst for the. oxidation of ammonia On the other hand, any one-skilled in the art may easily,

combine good catalysts-by simply testing comlbinatlons of catalysts proper and of basic carriers,-as has been shown in ths examIples.

.am aware that'magnesium oxid has already been proposed as an especially suitable contact carrier for the synthetical preparation of ammonia under high pressureaccording to Haber.

In the said process themagnesia is said to hold an exceptional osition as compared with other highly basic carriers, such as for instance calcium ox-id which is said to be absolutely unfit for use. However, it was the more impossible to form any conclusions concerning the behavior. of highly basic substances Eombined with the catalysts proper in the preparation of nitrogen oxids from ammonia which is absolutely -diflferntfr0m A.

i the synthesis of ammonia, as thefmagnesia,

1. The method containing oxygen and ammonia to the acclaimed a very .high

which had-been proved to be a good contact carrier for the synthesis according to Haber, I

does not for instancefurnish'a good carrier for; the synthetical preparation of ammonia by means of electric dlscharges.

The oxidation of ammonia in usin contact substances combine 50 I the in 30001 3.1106

with the "resent invention is carried out substantial y as follows:v A mixture of am--.

monia and air is passed over the contact substances placed in a ube, said substances be-. ing at first'heated 0 temperature between 400 and 700 degrees. After the reaction has been started, it will; continue 'of itself without further heating fron'i outside. By aid of -the new catalysts described 'and output of nitrogen oxide is-obtained. I claim 1 of oxidizing ammonia which consists insubjecting a gas mixture tion of catalysts formed-from highly basic catalytic active substances.

substances and substances capable of acceleratmg the oxldatlon of ammonia, said basic substances being in great excess of the 2. The method of oxidizing ammonia containing oxygen and ammonia to the-actlon of a trivalent metal-containmg 0x1dation catalyst associated Wlth magnesium oxid.

. 3. The method of oxidizing aniinonia -whi-ch consists in subjecting a gas mixture which consists in subjecting a gas mixture containing oxygen and ammonia to the action of catalysts formed from magnesium" oxid and substances capable of accelerating oxidation of the ammonia, the magnesium oxid being in great excess of the other substances. s

i 4:. The method of oxidizing ammonia which consists in subjecting a gas mixturecontaining oxygen and ammonia to the action of substances capable of accelerating the oxidation of ammonia, associated with highly basicsubstances,the basic substances belngTpresent in'a dense state.

he method of oxidizing ammon.ia

which consists in subjecting a gas mixturef containing oxygen and ammonia to the a'ction of substances capable of acceleratin theoxidation of ammonia, associated wit magnesium oxid, the magnesium oxid being present in a dense state.

6. The method of oxidizing ammonia" which consists in subjecting a gas mixture containing oxygen and ammonia to the action of substances capable of accelerating the oxidation of ammonia, associated with highly basic substances, the basic substances an artificially increased density.

h ng 7 he method of (oxidizing ammonia which consists in subjecting a gas mixture containing oxygen-and ammonia-ti) the action of substances capable of,accelerating the oxidation of ammonia, associated with magnesium oxid, ,the magnesium oxid having an artificially increased density.

.7 E}. The method of oxidizing ammonia which consists in subjecting a gas mixture containing oxygen and ammonia to the ac-- tion of substances capable of accelerating tion of substances capable of accelerating the oxidation of ammonia, associated With highly-basic substances, the'basic substances having been densified previously by treating them with metal salts and roasting the product. a

11. The method of oxidizing ammoniawhich consists in subjecting a gas mixture containing oxygen and ammonia to the action of substances capable of accelerating the oxidation of ammonia associated with magnesium. onid, the magnesium oxidhaving been denslfied previously by treating it with metal salts and roasting theproduct.

In testimonywhereof I' have signedmy 15 name to this SPQCIFlCatlOII in the presence of two subscribing Witnesses. I

DR. ALEXANDER CLASSEN.

Witnesses GERT UD RAMOUKERS HENRY GNADFLIEG. 

